<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Index Page</title>
</head>
<body>
<h2>我是主页</h2>
<p>
    {{ msg }}
</p>
{% if error_msg is not None %}
<span>{{ error_msg }}</span>
{% end %}
</body>
</html>